In a sealing process of automobile body parts in an automobile manufacturing line which includes a body-welding step, coating steps and assembly steps, automobile body parts, which are press molded, are built up by spot welding in the first body-welding step. In this step, gaps are formed in joining areas of the automobile body parts due to the distortion of the body panels between the welding spots. Therefore, a body or seam sealer is applied to the gaps for the purpose of water-proofing, dust-proofing, air-tightness and anti-rusting in the joining areas of the automobile body parts.
In such a sealing process, a body or seam sealer comprising a one-pack heat curable composition is typically used. In general, in the coating step following the body-welding step, the automobile body parts are showered, pretreated and electrodeposition coated followed by baking in an electrodeposition oven, and then a body sealer is applied to the gaps having the joining areas of the automobile body parts. Thereafter, the automobile body parts are conveyed to a body sealer oven and then to primer painting, middle painting and top painting steps. Finally, the automobile body parts are conveyed to the assembly step.
However, the conventional one-pack heat curable sealer composition requires a sealer oven to cure the composition, and it has a serious problem that it deteriorates the appearance of a top paint due to dusts during the application of the sealer composition.
In the process of the production of oil filters, a sealer composition is partially cured, namely, kiss-gelled with UV ray or a heat source to prevent the damage of the uncured sealer composition during conveying the filters to a curing oven, and then completely cured by heating (see, for example, JP-A-8-500531). However, this process additionally requires a UV-radiation apparatus or a heating apparatus as an energy source to partially cure the sealer composition, which is less advantageous from the viewpoint of equipment expenses and energy costs.